Extreme weather and rising seas threaten bases from Virginia to Guam. For the first time, a Republican House has voted to recognize that.

Kwajalein, a tiny atoll in the Marshall Islands, is home to a state-of-the-art radar installation called Space Fence. The U.S. government awarded Lockheed Martin a nearly $1 billion contract in 2014 to build the new system, meant to help protect U.S. satellites and spacecraft from space debris when it becomes operational next year.

There’s just one problem. Kwajalein is a mere 10 feet above sea level, putting Space Fence at high risk for frequent flooding as sea levels rise over the coming decades.

It’s one of many U.S. military installations threatened by climate change around the world. One study last year found that rising oceans threaten 128 military installations on the coasts, including naval facilities worth around $100 billion.

The Pentagon has been aware for years of the looming danger represented by climate change. But partisan infighting in Congress, budget sequestration, and the toxic nature of the climate debate have hamstrung the Defense Dept. from taking steps to protect key assets — or even identifying which facilities face the most serious threats.

This week, though, the Pentagon may have gotten a boost — from the unlikeliest of places. The Republican-controlled House retained an amendment to the 2018 defense funding bill affirming that “climate change is a direct threat to the national security of the United States.” It orders defense officials to draw up a report laying out which facilities would be most affected.

“This is a reflection that some Republicans at least are waking up to this reality and voting to affirm the work that DoD is doing,” said Andrew Holland, director of studies and senior fellow for energy and climate at the nonpartisan policy organization American Security Project.

Defense authorizations have included similar language before: In 2008, then-Sens. John Warner (R-Va.) and Hillary Clinton (D-N.Y.) included a similar amendment. But that was a Democratic-controlled Congress; this time, some 45 Republicans voted for the climate-change language, and lawmakers from both sides shot down an attempt to strike the focus on climate change.

“I think it’s maybe the beginning of a turning point in Congress,” Holland said.

For more than a decade, the Pentagon has been clear-eyed about the risks posed by climate change. Rising sea levels threaten coastal installations, while floods, famines, and droughts promise waves of instability and conflict across big chunks of the planet. Even in the climate-change denying Trump administration, Defense Secretary James Mattis has reiterated what is by now the Pentagon’s standard line.

‘‘I agree that the effects of a changing climate — such as increased maritime access to the Arctic, rising sea levels, desertification, among others — impact our security situation,’’ Mattis expressed in testimony prior to his confirmation.

But climate change is deeply polarizing in Congress, where many Republicans still believe it is a “hoax,” or not caused by human activities. That makes the issue “toxic” to Pentagon staffers who need to squeeze money out of Congress, said retired Rear Admiral David Titley, former naval chief oceanographer and now a professor at Pennsylvania State University. Officers tend to “run in the other direction when anyone says climate change,” afraid to appear before Congress to argue for more resources for fear that what funding they do have will be cut.

Years of sequestration have squeezed even the fundamentals of military readiness. And while the Obama administration talked up the security threats from climate change, additional funding never came.

“I don’t think the Department of Defense today could give you some sort of ranking [of facilities] that are most under threat,” said Titley. “Especially if you consider the issues — sea level rise, water stress, impact from wildfires — and crosscut that with the military value of that particular base.”

Rising seas, extreme weather, and water stress won’t just affect domestic military infrastructure. America’s ability to project power around the world — and particularly in the Middle East — is likely to be weakened if no action is taken. In a 2012 report, the American Security Project ranked the top five U.S. military facilities most at risk from climate change — Norfolk, Guam, Eglin in Florida, Bahrain, and Diego Garcia, a shown on the map below:

The latter is the most threatened high-value base. Located on a British atoll, the U.S. base on Diego Garcia is a major hub for operations in the Middle East, allowing large bombers to deploy without being based in Saudi Arabia or Qatar and giving expeditionary access to the Indian Ocean, Persian Gulf, and Red Sea. But due to its location on a low-lying atoll, it’s the most threatened of all.

“It legitimately could disappear in a certain amount of years,” said Holland.

Closer to home, the world’s biggest naval base is an even starker illustration of what lies in store. The Hampton Roads region of Virginia, headquarters of the Atlantic fleet, is already buffeted by increasingly extreme weather and frequent flooding. The sea there has already risen by more than a foot in the past 100 years, and the base currently floods about 10 times a year. It’s going to get much worse — the Union of Concerned Scientists estimates that Norfolk may flood 280 times a year by 2100.

Hampton Roads is a climate change “crucible,” retired Rear Admiral Ann Phillips, who previously headed a Navy task force on climate change, said at a July 12 House roundtable on climate change and the military. “We have nearly every climate-related challenge in our future.”

She noted that that crucial ship-repair facilities are located at sea level on the Elizabeth River.

“They are right there on the waterfront. The challenge becomes, how do you resolve this issue? Do you move them?” Or should the military start planning to build a wall that’s really needed, to keep out the rising seas and modifying dry docks to make them safer?

“Having that conversation openly is something that has not quite happened yet,” she added.

Titley is optimistic that such a conversation may finally take place. The bipartisan effort to keep climate change in the defense authorization could be a sign of the “end of the beginning” of climate debate, said Titley, who noted that more than 40 Republicans clambered on board.

“I think that’s huge,” he said.

Image credit: American Security Project

Correction, July 14, 2017: John Warner was a Republican senator from Virginia. A previous version of this article incorrectly identified him as a Democrat.

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